I think they are both good choices, you can't go wrong. Having coatings is nice but not a deal breaker if the glass is in good condition. If you can haggle the price for the Jaegers down a little bit then I would go that way other wise the choice is 50/50.

One other thing, the Istar cell has a collimation flange built in. A Jaegers cell does not, that may be an issue depnding on the design of your ota.

And, you don't know what the thickness of the airspace ring between the crown and flint should be, and it does matter. It could be anything from 0.002" to 0.25" or more. Anyone else have the same Jaegers lens they'd be willing to disassemble and measure the airspacer thickness for Russ? Otherwise, it's gonna be trial and error with different spacings.

Then there's the OD/ID compatibility with the loose lens elements and the $60 cell. If it is bored too small they won't fit and the cell would have to be bored out larger. If the lenses do fit in it, they'll still have to be edge-shimmed to keep them centered in the bore to within 0.002", preferably less.

Given all these unknowns, I think the IStar lens is the lower risk way to go. But if you're a real experimentalist, get the Jaegers and keep us posted on your progress!
Mike

Hey Russ:The incremental cost between a new,coated lens in a proper fitting cell and the Jaegers isn't much. If you're going to put time and $ into the new OTA you might as well build it around a known quantity.

Well, gents, after sleeping on it, I came to the same conclusion as you..... I have a fond memory of a Jaegers 6" scope, as one was the first real scope I ever looked through, the scope that turned me from casual to serious, but the spacing issue, and the cell issue - shimming's easy, but turning it out, especially if the keeper ring threads get involved - could be a nightmare.Istar objectives are not entirely without issues, but they seem more than willing to rectify problems, should they occur. With the Jaegers, I open the box, and hope for the best.thanks,Russ

Got one of the 6" f/10's too from Surplus Shed for $425.00 ($430.00 including shipping)! They even have the f/15's! Like most of my other telescope projects, I will be hosting its construction here on CN and on my website at The Vega Sky Center ... It will be dedicated to and named after my dearly departed wife, Gelinda.

I have a strong feeling that the lens elements are coated. Jaegers' old catalog ad list these objective as being coated. None were listed as uncoated. I believe there is a very fine coating on the lens elements, much like those on my 85mm/1333mm Jaegers objective, which was also listed as being uncoated prior to me purchasing it. Once I receive my 6" f/10 achromat, I will confirm if it has a coating and report back.

I tend to favor the classics. If you are still cogitating about the jaegers and want to know about spacers (and if jaegers used a standard thickness for all their lenses), I have one and would be willing to take it out of the cell and measure the spacer for you.

I do have a 6" f/10 in an original Jaegers cell. But now that I think about it, the 6" f/15 only had 3 foil spacers separating the elements. That was in a custom cell. I also have a 6" f/5 Jaegers in a Jaegers cell. I've never had it apart, but it would be easy enough to look at it and the f/10 to see if they've got foil spacers as well.

And there are other CNers with Jaegers scopes. Maybe one of them (like Clint Whitman?) knows more about spacers here than I do.

"Not all Jaegers lenses were that good. One of our guys here has a 6"F15 that was made in the later years when the old man had retired and someone else ran the business. This lens is very poor with lots of zones and poor figure."

When you buy surplus you always need to remember that there is a reason these lenses are surplus. Perhaps they were never coated because they were not up to standard.

Fred has always been good to deal with at SS but I would want some reassurance that I wouldn't get stuck with a sup-par piece of glass.

"Not all Jaegers lenses were that good. One of our guys here has a 6"F15 that was made in the later years when the old man had retired and someone else ran the business. This lens is very poor with lots of zones and poor figure."

When you buy surplus you always need to remember that there is a reason these lenses are surplus. Perhaps they were never coated because they were not up to standard.

Fred has always been good to deal with at SS but I would want some reassurance that I wouldn't get stuck with a sup-par piece of glass.

dan

A dice throw to be sure. While a totally different animal, my own Jaegers 6" f/5 lens was disappointing at 83x (9 mm Nagler), not even considering the color. That's only 14x per inch. An old friends 6" f/8 Jaegers was likewise not a stunner.

It looks like the surplus lenses turning up are priced accordingly, about on par with the Chinese achromats. I think I would go the extra $500 to get a new D&G lens. The extra money gets you MgFl coatings, a choice of focal length, an adjustable cell - and very low risk and quality question marks. And by the time Barry delivers, you can have the rest of the project put togther

I picked up a 6" f15 set with a flat so I can do a double-pass ronchi test to get the spacing and rotation of the elements sorted out and verify with an artificial star. It will take a while but I'll post the process here if I have success. I re-spaced a 127mm objective I'd purchased surplus seconds and the performance was better than what the star test predicted.

I'm at an advantage because I have an OTA and mount at the ready!

I'll say this, I don't expect much as I am a skeptic about why these weren't made into complete units in the first place. I have a feeling that when they were being produced, one would have a tray of crowns and a tray of flints and the optician would find the best combination by trying out different elements. Just picking a crown and flint sight-unseen will be a bit of an adventure.

If I didn't partake in the back of my mind I'll always think about why I didn't take a chance!

If I can get a decent image I'll compare it side-by-side with my Istar objective and keep the winner...

Just in case I picked up a 4" f15 coated and mounted... that is the steal of the lot if you ask me, but we love our aperture around here, don't we?

Wow! That's a great price for the 103/1575 lens! If I weren't over extending for my upcoming ISTAR scope, I would definitely be going for one of those. Hmmmm, Mom's been looking for something to get me as a belated birthday present. I wonder

Shawn and AllJagers Optical always offered most of its objectives as coated or uncoated, and 'loose' or in a cell. The only Jaegers lens that I have looked through is my own 105mm f15 and it has proven to be a great little lens. I was looking forward to the Surplus Shed sales of the Jaegers stuff that they picked up, but now I'm not sure? If you get one test it immediately (double pass Ronchi should be enough) so that you can return it if it doesn't measure up. Still the prices that I am starting to see from them are sorta high for an unknown vintage of what used to be very fine optics.

Yes, it's not dirt cheap, but low enough to take a chance. SS gives 10 days after receiving the item to evaluate and return for full refund if desired. I've returned some things and SS refunded my Paypal payment no problem, and full amount. I think that the lens would be as least as good as the mass produced Chinese glass that's being bought- some ain't too good.

Also, I forgot to mention Roland Christen's statement. If you have ever met him (and I have) you need to understand that he is not going to speak well of anything that does not come near to optical perfection as possible; so the comment on Jaegers is understandable. Whatever glass comes from his shop is going to be as good as possible, and that is slow to make. So you are not going to get an AP lens out of a Jaegers shop, no matter what you paid. So if you can live without 100X per inch of diameter, than maybe a Jaegers might be OK.

Here is a picture of the 4" f/15 Jaegers lens I just purchased from Surplus Shed being tested via Double pass autocollimation. The pictures is taken on the outside of focus. A perfect lens would show perfectly straight lines. This one has the lines curving inward indicating overcorrection of around 1/4 wave.

- Dave

Attached Files

Just to compare, here is a picture of a very good 3" f/15 Selsi objective from $60 Ebay telescope with about 1/10 wave error. Note the straightness of the ronchi lines. I can barely detect any bowing of the Ronchi lines as I pass from inside to outside focus. While on the Jaegers lens the bowing is very easy to see.